The entire didclosure of Japanese Patent Applicaiton No. 2000-242367 filed on Aug. 10, 2000 including specification, claims, drawings and summary is incorporated herein by reference in its entirety.
1. Field of the Invention
This invention relates to a laser beam machining head and a laser beam machining apparatus equipped with it, which are useful when applied in performing laser beam welding and arc welding at the same time.
2. Description of the Related Art
Among welding techniques for joining metals together are laser beam welding and arc welding. Laser beam welding is performed using a CO2 laser oscillator or a YAG laser oscillator. CO2 laser light has to be mirror transmitted, and thus its adjustment is laborious, while YAG laser light can be transmitted by an optical fiber. Under these circumstances, expectations are rising for laser beam welding using a YAG laser oscillator. Arc welding comes in types, including gas shielded consumable electrode arc welding (GMA welding) such as MIG welding, and gas shielded non-consumable electrode arc welding such as TIG welding.
Since laser light is condensed by optical instruments to give a high energy density, laser beam welding achieves deep weld penetration in a narrow range of melting. With arc welding such as GMA welding (MIG welding, etc.) or TIG welding, on the other hand, the arc spreads in a relatively broad range, thus performing welding of a wide bead range, and enabling welding with a high groove tolerance. In recent years, therefore, methods for simultaneously performing laser beam welding and arc welding have been studied in attempts to carry out welding with a wide welding range and a deep weld penetration.
A laser beam machining head, which performs laser beam welding and arc welding simultaneously, has a configuration, for example, disclosed in Japanese Unexamined Patent Publication No. 1998-216972. As shown in FIG. 11, this laser beam machining head performs laser beam welding and arc welding by applying laser light 3 from a laser beam welding head 2 to a portion 1a, to be welded, of a base material 1, and simultaneously applying an arc discharge from an electrode 5 of a GMA welding head 4, while jetting a shielding gas at the portion 1a from a gas jet nozzle 6. However, this laser beam machining head is large in size as a whole, since the laser beam welding head 2 and the GMA welding head 4 are independent in the laser beam machining head. Moreover, it is tiresome to keep the relative positional relationship between the laser beam welding head 2 and the GMA welding head 4 always constant in response to a change in the welding position or the welding posture. Thus, the laser beam machining head is not suitable, particularly, for three-dimensional machining by a robot.
The inventors of the present invention proposed in Japanese Unexamined Patent Publication No. 1999-156573 a laser beam machining head capable of solving the above-described problems. In this laser beam machining head, as shown in FIG. 12 of the present drawings, laser light 12 transmitted by an optical fiber 11 is reflected by a convex roof mirror 13 and a concave roof mirror 14, and divided thereby into two divisional beams, a first divisional laser beam 12a and a second divisional laser beam 12b, with a space portion 17 being formed therebetween. These divisional laser beams 12a and 12b are focused by a focusing lens array 15 onto a portion to be welded. The concave roof mirror 14 and the focusing lens array 15 are perforated, at the center thereof, with through-holes 14a and 15a, respectively. An electrode holding pipe 16 for holding an arc electrode, such as a TIG electrode or a GMA electrode, is inserted through the through-holes 14a, 15a, whereby the arc electrode held by the electrode holding pipe 16 is located in the space portion 17 between the divisional laser beams 12a and 12b and rendered coaxial with these laser beams. With the above-mentioned conventional coaxial laser beam machining head, the through-holes 14a and 15b are provided in the concave roof mirror 14 and the focusing coaxial arrangement takes much time, effort and expense, and the sites of the through-holes 14a, 15b are easily damaged. Furthermore, the convex roof mirror 13 and the concave roof mirror 14 are used to divide the laser light 12 into two beams, but these concave and convex roof mirrors 13 and 14 are very expensive.
The present invention has been accomplished to solve the above problems, and its object is to provide a coaxial laser beam machining head which is small in size, free from the risk of damaging optical instruments, and inexpensive, and a laser beam machining apparatus having this head.
A laser beam machining head, as a first aspect of the present invention for attaining the above object, comprises:
one collimating optical system for making laser light into a parallel beam;
a first reflecting mirror for reflecting part of the laser light made into the parallel beam by the collimating optical system to divide the laser light into two beams, a first divisional laser beam and a second divisional laser beam;
a second reflecting mirror for further reflecting the first divisional laser beam reflected by the first reflecting mirror to form a space portion between the first divisional laser beam and the second divisional laser beam;
one focusing optical system for focusing the first divisional laser beam and the second divisional laser beam onto a portion to be machined; and
a tip machining portion of machining means disposed in the space portion between the first divisional laser beam and the second divisional laser beam coaxially with the laser beams.
The above laser beam machining head of the first aspect is very small in size, inexpensive, and free from the risk of damage to the optical instruments, in comparison with the conventional laser beam machining head. This laser beam machining head is so small in size that it can be easily mounted, for example, to a multi-axis NC robot. Moreover, the tip machining portion of the machining means and the laser light (the first and second divisional laser beams) are coaxial. Thus, the laser beam machining head can be easily positioned and moved to an arbitrary position by the multi-axis NC robot, and three-dimensional machining can be performed with ease. Also, if the tip machining portion of the machining means is a GMA electrode, coaxial welding by this GMA electrode and the laser light makes welding at a very high speed possible. In addition, irradiation with laser light can stabilize an arc. Thus, welding of an SUS material or a high Cr material in a pure Ar gas atmosphere becomes possible, without the use of a special wire.
A laser beam machining head as a second aspect of the invention is the laser beam machining head of the first aspect, wherein
the second reflecting mirror is rendered normally and reversely rotatable, whereby spacing between a focused tip of the first divisional laser beam and a focused tip of the second divisional laser beam is adjustable.
According to the laser beam machining head of the second aspect, the rotation angle of the second reflecting mirror is set as desired to widen the spacing between the focused tip of the first divisional laser beam and the focused tip of the second divisional laser beam to a suitable degree, whereby a base material with a broad gap width can be welded.
A laser beam machining head as a third aspect of the invention is the laser beam machining head of the first aspect, wherein
the first reflecting mirror is rendered movable, whereby the division ratio for the first divisional laser beam and the second divisional laser beam can be adjusted, and the second reflecting mirror is rendered normally and reversely rotatable, whereby the spacing between the focused tip of the first divisional laser beam and the focused tip of the second divisional laser beam can be adjusted.
According to the laser beam machining head of the third aspect, the moving position of the first reflecting mirror is set as desired to decrease the proportion of the first divisional laser beam to a suitable degree and increase the proportion of the second divisional laser beam to a suitable degree, and the rotation angle of the second reflecting mirror is set as desired to widen the spacing between the focused tip of the first divisional laser beam and the focused tip of the second divisional laser beam to a suitable degree, whereby the second divisional laser beam is first applied to the base material with a deep weld penetration, and then the first divisional laser beam is applied to form an adequate bead. On this occasion, satisfactory welding without porosity (voids) can be performed.
A laser beam machining head as a fourth aspect of the invention is the laser beam machining head of the first, second or third aspect, wherein
the optical axis of the collimating optical system and the optical axis of the focusing optical system are displaced in a direction perpendicular to the optical axes, whereby the collimating optical system is moved over toward one side relative to the focusing optical system so that the first divisional laser beam reflected by the first and second reflecting mirrors is entered into the other side of the focusing optical system.
According to the laser beam machining head of the fourth aspect, as compared with the agreement between the optical axis of the collimating optical system and the optical axis of the focusing optical system, the first divisional laser beam and the second divisional laser beam can be focused even by the focusing optical system of a smaller diameter, and the entire laser beam machining head can be made smaller in size.
A laser beam machining head as a fifth aspect of the invention comprises:
one collimating optical system for making laser light into a parallel beam;
a reflecting mirror for reflecting part of the laser light made into the parallel beam by the collimating optical system to withdraw the part of the laser light out of a body of the laser light, thereby forming a space portion in the body of the laser light;
one focusing optical system for focusing the body of the laser light, where the space portion has been formed, onto a portion to be machined; and
a tip machining portion of machining means disposed in the space portion of the body of the laser light coaxially with the body of the laser light.
The laser beam machining head of the fifth aspect is very small in size, inexpensive, and free from the risk of damage to the optical instruments, in comparison with the conventional laser beam machining head. This laser beam machining head is so small in size that it can be easily mounted to a multi-axis NC robot. Moreover, the tip machining portion of the machining means and the body of laser light are coaxial. Thus, the laser beam machining head can be easily positioned and moved to an arbitrary position by the multi-axis NC robot, and three-dimensional machining can be performed with ease. Also, if the tip machining portion of the machining means is a GMA electrode, coaxial welding makes welding at a very high speed possible. In addition, welding of an SUS material or a high Cr material in a pure Ar gas atmosphere becomes possible.
A laser beam machining head as a sixth aspect of the invention comprises:
one collimating optical system for making laser light into a parallel beam;
a first reflecting mirror for reflecting part of the laser light made into the parallel beam by the collimating optical system to withdraw the part of the laser light out of a body of the laser light, thereby forming a space portion in the body of the laser light;
a second reflecting mirror located outside the body of the laser light and adapted to reflect the part of the laser light reflected by the first reflecting mirror so as to be parallel to the body of the laser light and be in contact with or in proximity to the outer peripheral surface of the body of the laser light;
one focusing optical system for focusing the body of the laser light, where the space portion has been formed by the first reflecting mirror, and the part of the laser light reflected by the first and second reflecting mirrors, onto a portion to be machined; and
a tip machining portion of machining means disposed in the space portion of the body of the laser light coaxially with the body of the laser light.
The laser beam machining head of the sixth aspect is very small in size, inexpensive, and free from the risk of damage to the optical instruments, in comparison with the conventional laser beam machining head. This laser beam machining head is so small in size that it can be easily mounted to a multi-axis NC robot. Moreover, the tip machining portion of the machining means and the body of laser light are coaxial. Thus, the laser beam machining head can be easily positioned and moved to an arbitrary position by the multi-axis NC robot, and three-dimensional machining can be performed with ease. Also, if the tip machining portion of the machining means is a GMA electrode, coaxial welding makes welding at a very high speed possible. In addition, welding of an SUS material or a high Cr material in a pure Ar gas atmosphere becomes possible. Furthermore, part of the laser light taken out of the body of the laser light by the first reflecting mirror is further reflected by the second reflecting mirror, and focused to the portion to be machined, together with the body of the laser light, by the focusing optical system. Thus, the energy of the laser light is not wasted, but can be effectively used, minimizing a loss of the laser light.
A laser beam machining head as a seventh aspect of the invention is the laser beam machining head of the sixth aspect, wherein
the first reflecting mirror is inserted into the laser light, which has been made into the parallel beam by the collimating optical system, along a diametrical direction of a cross sectional plane of the laser light and obliquely relative to the optical axis of the laser light, and is also inclined in a direction perpendicular to the direction of insertion of the first reflecting mirror, whereby part of the laser light is reflected obliquely to the outside of the body of the laser light.
According to the laser beam machining head of the seventh aspect, part of the laser light taken out of the body of the laser light is located just beside the body of the laser light. Thus, as compared with part of the laser light being located at a position displaced from the position just beside the body of the laser light, the diameter of the focusing optical system can be rendered smaller, and the entire laser beam machining head can be made smaller in size.
A laser beam machining head as an eighth aspect of the invention is the laser beam machining head of the sixth or seventh aspect, wherein
the optical axis of the collimating optical system and the optical axis of the focusing optical system are displaced in a direction perpendicular to the optical axes, whereby the collimating optical system is moved over toward one side relative to the focusing optical system so that part of the laser light reflected by the first and second reflecting mirrors is entered into the other side of the focusing optical system.
According to the laser beam machining head of the eighth aspect, as compared with the agreement between the optical axis of the collimating optical system and the optical axis of the focusing optical system, the body of the laser light and part of the laser light can be focused even by the focusing optical system of a smaller diameter, and the entire laser beam machining head can be made smaller in size.
A laser beam machining head as a ninth aspect of the invention is the laser beam machining head of the first, second, third, fourth, fifth, sixth, seventh or eighth aspect, wherein
the tip machining portion of the machining means is a GMA electrode, a TIG electrode, a filler wire, an assist gas nozzle, or a powder nozzle.
The laser beam machining head of the ninth aspect is so small in size that it can be easily mounted to a multi-axis NC robot. Moreover, the laser beam machining head can be easily positioned and moved to an arbitrary position by the multi-axis NC robot. Furthermore, the laser beam machining head is inexpensive, and free from the risk of damaging the optical instruments.
A laser beam machining head as a tenth aspect of the invention is the laser beam machining head of the first, second, third, fourth, fifth, sixth, seventh or eighth aspect, wherein
the tip machining portion of the machining means is an assist gas nozzle, and the assist gas nozzle is a divergent nozzle.
According to the laser beam machining head of the tenth aspect, the assist gas can be jetted at a very high speed, so that the cutting speed or the drilling speed increases markedly.
A laser beam machining apparatus as an eleventh aspect of the invention comprises:
the laser beam machining head of the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth or tenth aspect;
a laser oscillator for oscillating laser light;
laser light transmission means for transmitting the laser light oscillated by the laser oscillator to the laser beam machining head; and
laser beam machining head moving means for positioning and moving the laser beam machining head to an arbitrary position.
The laser beam machining apparatus of the eleventh aspect is an inexpensive laser beam machining apparatus with excellent ability at machining, such as welding or cutting.